Severe Functional Disturbances Need Not be Accompanied by Significant Structural Changes

Severe Functional Disturbances Need Not be Accompanied by Significant Structural Changes

A direct relationship between disordered function and disordered structure is not always present and there may be very severe functional disturbances without any significant structural changes being present. A striking example of this has been of the worst scourges of humankind, yet it is caused by an organism, Vibrio cholera, that cannot either destroy the lining cells of the gut wall or even penetrate between them. There is no microscopic evidence that the organism damages any tissue. However, if untreated, more than half of the infected people will die from the dehydration and electrolyte disturbances that are V.Cholerae causes. This diarrhea occurs because the epithelial lining cells of the intestine respond to a toxin, secreted by the organism, which behaves in the same way as a normal hormonal regulatory signal. When food is delivered to the small intestine, a peptide binds to a receptor site on the luminal membrane of the small intestinal epithelial cell and stimulates the adenylate cyclase system, with the result that about 2 litres of alkaline fluid are pumped into the small intestine.